Its standard definition is a difficulty in reading and writing in spite of normal or above-average intelligence and cognitive abilities.

The word "dyslexia" comes from the Greek words δυς- dys- ("impaired") and λέξις lexis ("word"). People are often identified as dyslexic or dyslectic when their reading or writing problems cannot be explained by a lack of intellectual ability, inadequate instruction, or sensory problems such as poor eyesight.

The term dyslexia is also sometimes used to refer to the loss of reading ability following brain damage. This form of dyslexia is more often referred to as either acquired dyslexia or "alexia". Dyslexia primarily impacts reading and writing abilities; however, other difficulties have been reported including deficits in processing spoken language[1] as well as non-language difficulties.[2]

Despite popular belief, dyslexia is not caused by reversing the order of letters in reading, nor is it a visual perception deficit that involves reading letters or words backwards or upside down.

Evidence that dyslexia is a neurological or brain-based condition is substantial. Research also suggests an association with biochemical and genetic markers.[3][4][5] Some question whether the term dyslexia is so fraught with popular misconceptions that it should be dropped altogether and replaced with the term Reading Disorder or Reading Disability (RD). Because difficulty in "breaking the code" of sound-letter association (reading acquisition) can be seen as being on a continuum, some believe the term dyslexia should be reserved for the two to five percent most severely affected with RD. Moreover, dyslexia is not always the culprit in a child's not learning to read. Poor teaching methods can leave non-dyslexic children with poor reading skills.[6]

Contents

The term 'dyslexia' was coined in 1887 by Rudolf Berlin.[7] He used the term to refer to a case of a young boy who had a severe impairment in learning to read and write in spite of showing typical intellectual and physical abilities in all other respects.

Several years later, W. Pringle Morgan, a British physician, from Seaford, East Sussex, England published a description of a reading-specific learning disorder in a letter to the British Medical Journal. His letter described the case of a boy named Percy who, at age 14, had not yet learned to read, yet he showed normal intelligence and was generally adept at other activities typical of children of that age.

Some early researchers believed dyslexia stemmed from a visual deficit. This notion has persisted in popular culture, where it is falsely believed that dyslexia equates to reading words backwards or upside-down.

A key early researcher in dyslexia was Samuel T. Orton. Orton coined the term strephosymbolia (meaning 'twisted signs') to describe his theory that individuals with dyslexia had difficulty associating the visual forms of words with their spoken forms.[8] Orton observed that reading deficits in dyslexia did not seem to stem from strictly visual deficits.[9] He also believed that dyslexics were disproportionately left-handed, although this finding has been difficult to replicate.[10]

In the 1970s, a new hypothesis, based in part on Orton's theories, emerged that dyslexia stems from a deficit in phonological processing or difficulty in recognizing that spoken words are formed by discrete phonemes (for example, that the word CAT comes from the sounds [k], [æ], and [t]). As a result, affected individuals have difficulty associating these sounds with the visual letters that make up written words. Key studies of the phonological deficit hypothesis include the finding that the strongest predictor of reading success in school age children is phonological awareness,[11] and that phonological awareness instruction can improve reading scores in children with reading difficulties.[12]

Thomas G. West, towards the end of the 20th century, suggested that many dyslexics are visual spatial thinkers who are wired for the big picture — designed to process information in pictures rather than words. West believed that our education system is inadvertently biased against the "Einstein gene", and thereby all our most original and gifted thinkers. To support this view he has examined the difficult early experiences within education of five Nobel prize winners. or near-winners: Einstein, Edison, Marconi, Churchill and Faraday.

West's theory is echoed in the work of Ronald Dell Davis, author of The Gift of Dyslexia, who describes dyslexia as the outgrowth of a primarily picture-thinking mind. Davis posits that the symptoms associated with dyslexia arise from disorientation that results from confusion over language symbols. This view has also been supported indirectly by the research of by Linda Silverman, author of Upside Down Brilliance - the title reflects the counter-intuitive experiences of those who find the easy tasks difficult and hard tasks easy. Echoes of this theory can be traced to the emerging discipline of Neuro-linguistic Programming.

Dyslexia is widely accepted to be a specific learning disability. That is, dyslexia has biological traits that differentiate it from other learning disabilities. However, the specific definition of dyslexia varies somewhat across communities.

Dyslexia or Reading Disorder is defined in the Diagnostic and Statistical Manual of Mental Disorders DSM-IV as reading achievement that falls substantially below expected levels given an individual's age and education. The reading deficit should be sufficiently severe as to interfere with everyday activities requiring reading (e.g., schoolwork or employment). Finally, the reading deficit cannot be strictly due to a sensory disorder; for instance, it cannot be strictly due to vision problems that prevent an individual from seeing words on a page.

Several national and international organizations have also set out definitions of dyslexia as follows:

The World Health Organization (WHO)

"A disorder manifested by difficulty learning to read, despite conventional instruction, adequate intelligence and sociocultural opportunity. It is dependent upon fundamental cognitive disabilities which are frequently of constitutional origin".
ICD-10, The International Statistical Classification of Diseases and Related Health Problems, tenth revision ICIDH-2, The International Classification of Impairments, Activities, and Participation

US National Institute of Child Health and Human Development (NICHD) / International Dyslexia Association

The Government of Canada’s Health Portal links its description to the BC HealthGuide web site using their definition. Dyslexia is defined here having a difficulty with the alphabet, reading, writing, and spelling in spite of normal to above average intelligence, conventional teaching, and adequate sociocultural opportunity. Dyslexia is thought to be both genetic and hereditary. Dyslexia is not caused by poor vision. Dyslexia is identified following psychological and educational tests that determine language and other academic abilities, IQ and problem-solving skills, and is only identified if the reading disability is not a result of another condition.

The British Dyslexia Association

Dyslexia is a difference in the brain area that deals with language. It affects the underlying skills that are needed for learning to read, write and spell. Brain imaging techniques show that dyslexic people process information differently. In a report on the House of Lords Dyslexia debate which took place on December 7, 2005, the government confirms that dyslexia is not a myth.

Developmental dyslexia appears to be the result of differences in affected individuals' neural organization for language and reading. Developmental dyslexia also appears to have a genetic component, such that it can tend to occur in multiple members of the same family. Reading difficulties in dyslexia can vary in their severity. The condition is not restricted to childhood, and can persist through adulthood. In addition, while early reports suggested dyslexia is more prevalent in boys, more recent studies have indicated it is not sex-linked, and occurs both in boys and girls with equal frequency.

Much of the current scientific research focuses on the hypothesis that dyslexia stems from a deficit in phonological awareness. This hypothesis suggests that affected individuals have difficulty analyzing the words they hear into discrete segments (such as phonemes), which in turn leads to difficulty learning spelling-sound correspondences.

Other research focuses on the theory that dyslexia results from a magnocellular deficit related to visual processing,[17] or that it is related to a cerebellar deficit.[18]
Most recently, researchers have suggested that the underlying deficit is with the brain's ability to filter irrelevant data, relying on studies showing that the performance of dyslexic subjects deteriorates markedly in distraction or noise filled settings to support a perceptual noise exclusion hypothesis.[19]

Researchers studying the brains of dyslexics have found that during reading tasks, dyslexics show reduced activity in the left inferiorparietal cortex. It is anecdotally claimed that it is not that uncommon for dyslexics who have trained themselves to cope with their affliction to develop uncannily efficient visual memories which aid in reading and comprehending large quantities of information much faster than is typical. Some dyslexics may show a natural dislike of reading and, as a consequence, compensate by developing unique verbalcommunication skills, interpersonal expertise, visual-spatial abilities, and leadership skills.

In 1979, anatomical differences in the brain of a young dyslexic were documented. Albert Galaburda of Harvard Medical School noticed that the language center in a dyslexic brain showed microscopic flaws known as ectopias and microgyria. Both affect the normal six-layer structure of the cortex. An ectopia is a collection of neurons that have pushed up from the lower layers of the cortex into the outermost one. A microgyrus is an area of cortex that includes only four layers instead of six. These flaws affect connectivity and functionality of the cortex in critical areas related to auditory processing and visual processing, which seems consistent with the hypothesis that dyslexia stems from a phonological awareness deficit.

Another study regarding genetic regions on chromosomes 1 and 6 have been found that might be linked to dyslexia. Presenting the argument, dyslexia is a conglomeration of conditions that all affect similar and associated areas of the cortex.

Formal diagnosis of dyslexia is made by a qualified professional, such as a neurologist or an educational psychologist. Evaluation generally includes testing of reading ability together with measures of underlying skills such as tests of rapid naming, to evaluate short term memory and sequencing skills, and nonword reading to evaluate phonological coding skills. Evaluation will usually also include an IQ test to establish a profile of learning strengths and weaknesses. However the use of a "discrepancy" between full scale IQ and reading level as a factor in diagnosis has been discredited by recent research. It often includes interdisciplinary testing to exclude other possible causes for reading difficulties, such as a more generalized cognitive impairment or physical causes such as problems with vision or hearing.

Recent advances in neuroimaging and genetics provide evidence that could help identify children at risk of dyslexia before they learn to read in the future. However such tests have not yet been developed.

The following characteristics have been adapted from R. D. Davis, 37 Common Characteristics of Dyslexia.[20]

Because dyslexia primarily affects reading while sparing other intellectual abilities, affected individuals might be categorised as not "behind enough" or "bad enough" to receive additional help in a school setting.

Might feel dumb and have poor self-esteem, and might be easily frustrated and emotional about school reading or testing.

Contrary to how it has been portrayed in the popular press, individuals with dyslexia do not perceive words backwards or upside down. In fact, visual problems are typically ruled out before a diagnosis of dyslexia can be made. Early studies of dyslexia did focus on the possibility that dyslexia is caused by visual difficulties, however very little evidence was found to support this theory. Likewise, there is little evidence that visual training provides effective treatment.[21]

A popular theory in the 1970s suggested dyslexics may have Meares-Irlen Syndrome, a visual deficit in which the glare of the white page against black letters causes the words to shake, shiver, spin, etc. after a few minutes of reading. The proposed treatment was the use of colored plastic overlays that were thought help anchor the words to the page. This treatment has fallen out of favor as scientific studies have failed to support these claims. (See link below to asfedia).

Letter order - Dyslexics may also reverse the order of two letters especially when the final, incorrect, word looks similar to the intended word (e.g., spelling "dose" instead of "does").

Highly phoneticized spelling - Dyslexics also commonly spell words inconsistently, but in a highly phonetic form such as writing "shud" for "should". Dyslexic individuals also typically have difficulty distinguishing among homophones such as "their" and "there".

Reading — Due to dyslexics' excellent long term memory, young students tend to memorize beginning readers, but are unable to read individual words or phrases.

Because of literacy problems, an individual with dyslexia may have difficulty with handwriting. This can involve slower writing speed than average or poor handwriting characterised by irregularly formed letters.

Some studies have also reported gross motor difficulties in dyslexia, including motor skills disorder. This difficulty is indicated by clumsiness and poor coordination. The relationship between motor skills and reading difficulties is poorly understood but could be linked to the role of the cerebellum in the development of reading and motor abilities.[22]

Dyslexia should not be confused with dyscalculia, a learning disability marked by severe difficulties with mathematics.
Individuals with dyslexia can be gifted in math while having poor reading skills. However, in spite of this they might have difficulty with word problems (i.e., math problems that rely on written text rather than numbers or formulas).
It is also possible that individuals with dyslexia have difficulty with multiplication tables, and other mathematics which involve remembering the order in which numbers appear.

The term "visual dyslexia" is sometimes used to refer to a physical problem with eyesight. This is considered by some specialists [3] to be as much a physical condition as myopia and hyperopia. Treatment to address the physical symptoms may include eye exercises or corrective lenses.[How to reference and link to summary or text]

The child with vision problems may underachieve in academic work or in social environments. Self-esteem is lowered and antisocial behaviour is common. At school, reading and comprehension tests will cause problems and psychometric testing may not be reliable unless visual perceptual problems have also been considered and addressed.

However, the term "visual dyslexia" has historically been used to distinguish among types or symptom profiles of developmental dyslexia, which has a cognitive or neurological basis. In that context, "visual dyslexia" may also be called "surface dyslexia" or "dyseidetic dyslexia" and is used to refer to a form of dyslexia where the primary difficulty is with visual discrimination, visual memory, visual sequencing, left-right scanning and in rapid visual recognition of words. This form of dyslexia is distinguished from "auditory dyslexia" or "phonological dyslexia", where the primary difficulty is with discriminating speech sounds, in sound blending, auditory sequencing and serial memory, and in phonological awareness.[23]
Optometric treatment, including vision therapy or specialized lenses, is not sufficient to resolve reading problems that are a result of the dyseidetic form of developmental dyslexia, but can only be part of a multi-disciplinary approach.[24]

Dyslexia is a learning disorder. Its underlying cause is believed to be a brain-based condition that influences the ability to read written language. It is identified in individuals who fail to learn to read in the absence of a verbal or nonverbal intellectual impairment, sensory deficit (e.g., a visual deficit or hearing loss), pervasive developmental deficit or a frank neurological impairment. The following conditions are sometimes confused with dyslexia because they can also lead to difficulty reading:

Auditory Processing Disorder is a condition that affects the ability to encode auditory information. It can lead to problems with auditory working memory and auditory sequencing.

Dyspraxia is a neurological condition characterized by a marked difficulty in carrying out routine tasks involving balance, fine-motor control, and kinesthetic coordination. This is most common in dyslexics who also have Attention Deficit Disorder.

Verbal Dyspraxia is a neurological condition characterized by marked difficulty in the use of speech sounds, which is the result of an immaturity in the speech production area of the brain.

Dysgraphia is a neurological condition characterized by distorted and incorrect handwriting.

Dyscalculia is a neurological condition characterized by a problem with learning fundamentals and one or more of the basic numerical skills. Often people with this condition can understand very complex mathematical concepts and principles but have difficulty processing formulas and even basic addition and subtraction.

Scotopic Sensitivity, also known as Irlen Syndrome, is a sensitivity to certain wavelengths of light which interfere with proper visual processing.

In the United States, researchers estimate the prevalence of dyslexia to range from five to nine percent of school-aged children, though some have put the figure as high as 17 percent.[25][26]

Dyslexia's main manifestation is a difficulty in developing reading skills in elementary school children. Those difficulties result from reduced ability to associate visual symbols with verbal sounds. While motivational factors must also be reviewed in assessing poor performance, dyslexia is considered to be genetically influenced. Most scientific criteria for dyslexia exclude cases that can be explained as arising from environmental factors such as lack of education or sensory deficits.

Dyslexia can be substantially compensated for with proper therapy, training, and equipment.

Reported prevalence of dyslexia is much higher in English (about 5-6%) than Chinese. [Brian Butterworth and Joey Tang are in the Institute of Cognitive Neuroscience at University College London][How to reference and link to summary or text]

Some studies have concluded that speakers of languages whose orthography has a strong correspondence between letter and sound (e.g. Korean, Italian and Spanish) suffer less from effects of dyslexia than speakers of languages where the letter is less closely linked to the sound (e.g. English and French).[27]

In one of these studies, reported in Seymour et al.,[28] the word-reading accuracy of first-grade children of different European languages was measured. English children had an accuracy of just 40%, whereas among children of most other European languages accuracy was about 95%, with French and Danish children somewhere in the middle at about 75%; Danish and French are known to have an irregular pronunciation.

However, this does not mean that dyslexia is caused by orthography: instead, Ziegler et al.[29] claim that the dyslexia suffered by German or Italian dyslectics is of the same kind as the one suffered by the English ones, supporting the theory that the origin of dyslexia is biological. However, dyslexia has more pronounced effects on orthographically difficult languages.

In the United States, Canada, New Zealand and in the United Kingdom, some people say that there is a lack of adequate support and a general lack of interest in the learning disabilities of children in public schools. This has recently led to legal action by private parties against public schools in the United States and state schools in the United Kingdom. In English law, the recent case of Skipper v Calderdale Metropolitan Borough School (2006) EWCA Civ 238 the Court of Appeal applied Phelps v London Borough of Hillingdon (2001) 2 AC 619 as the landmark case on the failure to diagnose dyslexia (see duty of care in English law), and to hold that the appellant could pursue her claim against her school for humiliation, lost confidence, and lost self-esteem, and for loss of earnings following its failing to diagnose and treat her dyslexia despite the fact that, as Latham LJ. says at para 29:

"The extent to which her dyslexia could have been ameliorated or provided for will always remain uncertain, as will the extent to which that would have affected her performance in public examinations; the evidence that we have includes material to suggest that she, not surprisingly, reacted adversely to the break-up of her parents marriage when she was 15, in other words at a critical time in her education. Whether any improvement in her examination results would have led to her life taking a significantly different course will also be a matter for some speculation."

Some charitable organizations like the Scottish Rite Foundation have undertaken the task of testing for dyslexia and making training classes and materials available, often without cost, for teachers and students.[30][31][32]

In England and Wales, the failure of schools to diagnose and provide remedial help for dyslexia following the House of Lords decision in the case of Pamela Phelps has created an entitlement for students with dyslexia in Higher Education to receive support funded via the Disabled Students Allowance. Support can take the form of IT equipment (software and hardware) as well as personal assistance, also known as non-medical helper support. Dyslexic students will also be entitled to special provision in examinations such as additional time to allow them to read and comprehend exam questions.

"In some cases, people have 'coping strategies' which cease to work in certain circumstances (for example, where someone who stutters or has dyslexia is placed under stress). If it is possible that a person's ability to manage the effects of the impairment will break down so that these effects will sometimes occur, this possibility must be taken into account when assessing the effects of the impairment." — Paragraph A8, Guidance to the Definitions of Disability

Some disagreement exists as to whether dyslexia does indeed exist as a condition, or whether it simply reflects individual differences among different readers.

"The Dyslexia Myth" is a documentary that appeared as part of the Dispatches series produced by British broadcaster Channel 4.[33] First aired in September 2005, it claims to expose myths and misconceptions that surround dyslexia. It argues that the common understanding of dyslexia is not only false but makes it more difficult to provide the reading help that hundreds of thousands of children desperately need. Drawing on years of intensive academic research on both sides of the Atlantic, it challenged the existence of dyslexia as a separate condition, and highlighted the many different forms of reading style.

The documentary only focused on the reading difficulties that dyslexics encounter. As discussed in previous headings, dyslexia is more than a mere reading disability, and commonly includes symptoms that extend beyond reading difficulties. However, these symptoms are not included in the DSM-IV list of symptoms by which "Reading Disorder" is diagnosed.

The external links in this article or section may require cleanupPlease improve this article by removing excessive or inappropriate external links. Please remove this tag when this is done. This article has been tagged since January 2007. (talk)